Yep. It's got nothing to do with historical Vikings, anyway: they loved their hair (combs are found all over Viking archaeological sites), but they often wore it short, unlike the long-haired Anglo-Saxons. (Both is privilege, of course. Princelings could afford flowing long hair, peasants had to worry about it getting in the way.) The more relevant idea of the Viking in nineteenth-century romantic nationalism was long-haired, of course, hence the influence.

Sabbath were anti-hippies. They opposed their escapism and delusions of peace through love. Hippie culture was a tiny, short-lived movement that just happened to get a lot of attention.

Bullshit, Sabbath were definitely hippies; furthermore, they were absolute ardent advocates of escapism. What are so many of their early songs about? Reality? Did they acquire a notoriety for excessive drug use, often seen as the ultimate escapist activity.

Just because you like being high it doesn't mean you are ignoring inconvenient realities.

Theres a huge difference between 'liking being high' and the excessive drug use which Black Sabbath indulged in. But either way, do you think that hippies were just ignoring reality? To an extent, one of the clichés of hippie-ness has been the peace and love idea, but underpinning it was a drive for greater personal freedom which has largely been realised almost 50 years on. Hippies were able to normalise (to a degree) what was then considered deviance and Black Sabbath were riding that exact wave. I doubt that transgressives like Black Sabbath and metal and punk would have existed if it hippies hadn't come transgressing along before them. People write off hippies as being escapist whilst being utterly immersed in the reality that they helped BEGIN a movement towards.

If you really want to go back to where the long hair in rock music started you have to go back to rock'n'roll and rockabilly. These people had that distinguishable style of hair which bands in England adopted. If you look at early Beatles pictures they had that whole teddy bear look going. When the music industry kicked in and took The Beatles under their wing they told them to start wearing suits instead of leather and at the same time they stopped the whole rockabilly hair style, but they didn't cut their hair and just hair dried it. If we look at them today they didn't have long hair, but back then they were sort of ridiculed and it was quite controversial, but the whole mop-top hairdo really clicked in for all the other bands at that time. I don't know how it really started, but the image of the Beatles was really made up by the industry so that's where it really started.

After the big bands started to experiment with drugs in 1965 and started to be in peace with nature and so on, and as it is naturally for the hair to just grow, they stopped cutting their hair. It evolved with the whole hippy movement in 1967, when everybody took drugs and grew their hair to a modern metalhead length. That's where metal comes from whether we metalheads like it or not, we owe the hippies a lot. Experimentation happened along with all types of drugs, and we had people trying to play heavy like Jimi Hendrix some people call it "acid rock". Black Sabbath came from that environment and all of them had long hair, along with bunch of similar bands. And as Black Sabbath became a staple for all hard rock/heavy psych bands later on for a few good years their image came with that and so all these bands had long hair. Along with Hard Rock bands had long till the 90s, when rock bands started to have shorter hair, but it stayed with heavy metal mainly due to headbanging and such.